Apparatus for building tyres for vehicle wheels

ABSTRACT

An apparatus for building tyres for vehicle wheels are described. A substantially cylindrical carcass sleeve, having at least one carcass ply, includes consecutively adjacent strip-like elements laid one after the other around the circumferential extension of a substantially cylindrical deposition surface. Circumferentially consecutive strip-like elements laid one after the other form overlap zones along respective longitudinal edges superimposed on each other. Each overlap zone has, along a longitudinal extension thereof, terminal sections that are laterally opposite with respect to an intermediate section. The intermediate section of each overlap zone has greater width than the width of the terminal sections.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/907,096, filed on Jan. 22, 2016 which is the U.S. national stageentry of International Patent Application No. PCT/IB2014/062737, filedinternationally on Jun. 30, 2014 which, in turn, claims priority toItalian Patent Application No. MI2013A001299, filed on Aug. 1, 2013.Each of these applications are incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates to a process and an apparatus for buildingtyres.

More particularly, the invention is intended for a process and theequipment used for building a green tyre, to be subsequently subjectedto a moulding and vulcanising cycle, and intended for the tyre obtainedby the aforesaid process.

A tyre for vehicle wheels generally comprises a carcass structurecomprising at least one carcass ply having respectively opposite endflaps engaged with respective annular anchoring structures, integratedin the zones normally identified with the name of “beads”, having aninner diameter substantially corresponding with a so-called “fittingdiameter” of the tyre on a respective mounting rim.

The carcass structure is associated with a belt structure comprising oneor more belt layers, situated in radial superimposition with respect toeach other and with respect to the carcass ply, having textile ormetallic reinforcement cords with crossed orientation and/orsubstantially parallel to the direction of circumferential extension ofthe tyre. In radially outer position with respect to the belt structure,a tread band is applied, it too made of elastomeric material like othersemifinished products constituting the tyre.

Respective sidewalls made of elastomeric material area also applied inaxially outer position on the lateral surfaces of the carcass structure,each extending from one of the lateral edges of the tread band up to therespective annular anchoring structure to the beads. In the tyres of“tubeless” type, a covering layer impermeable to air, usually termed“liner”, covers the inner surfaces of the tyre.

Following the building of the green tyre actuated by assembling ofrespective components, a moulding and vulcanising treatment is generallyexecuted that is aimed to determine the structural stabilization of thetyre by means of cross-linking of the elastomeric compositions as wellas impart on the same a desired tread design and possible distinctivegraphical signs at the sidewalls of the tyre.

The terms “radial” and “axial” and the expressions “radiallyinner/outer” and “axially inner/outer” are used, making reference to theradial direction and to the axial direction of a forming support (orbuilding drum) used for building one or more components of the tyre. Theterms “circumferential” and “circumferentially” are instead used, makingreference to the annular extension of the aforesaid forming support.

The radial plane of the forming support is the plane comprising therotation axis thereof.

Analogously, the radial plane of the finished tyre or tyre beingprocessed is the plane comprising the rotation axis thereof.

With the term “elastomeric material” it is intended to indicate acomposition comprising at least one elastomeric polymer and at least onereinforcement filler. Preferably, such composition also comprisesadditives such as a cross-linking agent and/or a plasticizing agent. Dueto the presence of the cross-linking agent, by means of heating suchmaterial can be cross-linked, so as to form the final manufactured item.

With the term “elementary semifinished products” it is intended toindicate hereinbelow continuous elongated elements made of elastomericmaterial, textile and/or metallic rubberized cords, strip-like elements.By “strip-like element” it is intended a strip made of elastomericmaterial cut to size and comprising one or more textile or metallicreinforced cords, parallel, adjacent and substantially coplanar withrespect to each other. Such elementary semifinished products are adaptedto be used in a quantity suitable for composing one or more of theabove-described constituent elements of the tyre, without requiring thestorage of semifinished products.

By “continuous surface” relative to a building drum, it is intended asurface without interruption or in which possible openings (such asholes or grooves) are of size such that the elastomeric material of thesemifinished product that substantially rests thereon does not penetrateit. The possible openings each have for example an area less than orequal to about 300 mm² (e.g. groove of about 150 mm of axial extensionfor about 2 mm of width) and the set of the openings overall have anarea less than or equal to about 20%, preferably less than or equal toabout 15% of the total area of said continuous surface.

By “overlap width”, it is intended the size of the zone of mutualsuperimposition between two adjacent strip-like elements, measured alongthe circumferential extension of a deposition surface.

The document WO 2008/099236, on behalf of the same Applicant,illustrates a process and an apparatus for manufacturing tyres wherein acarcass sleeve is formed around an external surface of a building drum,according to an application diameter greater than the fitting diameterof the tyre. For such purpose, one or more dispensing members feed atleast one continuous elongated element made of elastomeric materialwhile the building drum is driven to rotate around its geometric axis,so as to form the liner on an external surface and on support surfacesof the building drum. Application members sequentially apply a pluralityof strip-like elements arranged transverse with respect to thecircumferential extension of the external surface, while the formingdrum is driven to rotate according to a step-by-step progression, inorder to form a carcass ply. Around each of the end flaps of the carcassply, an annular anchoring structure defining the fitting diameter iscoaxially engaged. An external sleeve comprising a belt structureassociated with a tread band is arranged in coaxially centered positionaround the carcass sleeve built on the aforesaid building drum. Thebuilding drum comprises a central section and two half-parts that areaxially movable with respect to the central section. By means of mutualaxial approaching of the two half-parts, the same carcass sleeve isshaped according to a toroidal configuration in order to determine theapplication thereof against a radially inner surface of the externalsleeve, according to a “process of building in a single step” or“single-stage process”.

The document WO 2009/068939, on behalf of the same Applicant,illustrates a process and an apparatus for manufacturing tyres wherein acarcass ply is built by means of the application of a plurality ofstrip-like elements on a radially outer deposition surface of a buildingdrum. An integer of strip-like elements to be applied is calculated as afunction of the width of such strip-like elements, of the overlap widthbetween two adjacent strip-like elements, of the extension of thedeposition surface.

The Applicant has observed that, in order to prevent possible damage onthe manufactured item being processed, it is opportune in the productionsystems of the above-described type that the internal surfaces of thecarcass structure are separated from the deposition surface before thestart of the mutual approaching of the half-parts of the building drum.This operation requires additional times in executing the process, sinceat least the carcass ply/plies impose considerable resistance to thedilatation that they must undergo in order to be separated from thedeposition surface.

The Applicant has therefore perceived the need to attain considerableimprovements in production processes, particularly in terms of reductionof the cycle-time required for executing the shaping and of increase ofthe qualitative constancy of the product.

In addition, in the scope of production processes of the illustratedtype, the Applicant has perceived the possibility to improve theperformances of the tyre in terms of fatigue strength and ride comfort.

More particularly, the Applicant deems that the performances in terms offatigue strength and ride comfort of a tyre can be improved if the tyreis conferred greater structural flexibility. For such purpose, theApplicant has perceived that the structural flexibility of the tyre inthe tyres built by means of the use of strip-like elements for obtainingthe carcass ply/plies (for example as illustrated in WO 2008/099236 andWO 2009/068939) is significantly affected by the width of the overlapbetween the strip-like elements themselves in the built carcassply/plies.

The Applicant has perceived that a limited width of the overlap betweencircumferentially contiguous strip-like elements can advantageouslycorrespond with a greater structural flexibility of the carcassstructure, particularly in the zones of the sidewalls extending from theaxially opposite edges of the belt structure up to in proximity to thebeads.

The Applicant has finally found that by reducing or cancelling the sizeof the overlap between circumferentially contiguous strip-like elementsin proximity to the sidewalls and/or beads of the tyre, it is possibleto attain significant quality improvements of the tyre itself and of thecorresponding building process, particularly in terms of reliability,fatigue strength and ride comfort, as well as of reduction of therequired cycle-time for executing shaping operations. According to theApplicant, it is still preferable to maintain an overlap of asufficiently large size in proximity to the intermediate portions of thelongitudinal extension of the strip-like elements, i.e. at the radiallymore outer zones of the toroidally-shaped carcass structure, in order toreduce the risk of undesired separations between circumferentiallycontiguous strip-like elements following the deformations induced duringshaping.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention relates to a processfor building tyres for vehicle wheels.

Preferably it is provided to form a substantially cylindrical carcasssleeve, comprising at least one carcass ply.

Preferably said at least one carcass ply is formed by layingconsecutively adjacent strip-like elements one after the other aroundthe circumferential extension of a substantially cylindrical depositionsurface.

Preferably circumferentially consecutive strip-like elements are laidone after the other to form overlap zones along respective longitudinaledges superimposed on each other.

Preferably each overlap zone has, along a longitudinal extensionthereof, terminal sections that are laterally opposite with respect toan intermediate section.

Preferably the intermediate section of each overlap zone has greaterwidth than the width of the terminal sections.

The Applicant deems that it is thus possible to attain an advantageouscontainment of the width of the overlap in the terminal portions of thecarcass sleeve, without having to also reduce the size of the overlap inthe central zones. The Applicant has indeed observed that the reductionof the width of the overlap in the terminal zones does not compromisethe structural integrity of the carcass sleeve, even for the purposes ofthe shaping thereof according to a toroidal configuration. Moreparticularly, the Applicant deems that the deformations and stressesinduced by the shaping operation are particularly concentrated in theintermediate zone of the axial extension of the carcass sleeve, where agreater circumferential and radial dilatation is required for bringingthe carcass ply in contact against the internal surface of the externalannular sleeve. On the contrary, towards the terminal zones thedeformations and consequent stresses are progressively reduced, up to inproximity to the beads of the tyre, which maintain a constant diametereven during shaping. The Applicant finally deems that the reduction ofthe width of the overlap in the terminal portions facilitates theoperations of mounting the tyre on the rim, due to a greaterdeformability of the beads.

According to a further aspect, the present invention relates to anapparatus for building tyres for vehicle wheels.

Preferably first forming devices are provided for, configured forforming a carcass sleeve on a building drum.

Preferably said first forming devices comprise laying devices configuredfor laying circumferentially consecutive strip-like elements around thecircumferential extension of a substantially cylindrical depositionsurface presented by the building drum.

Preferably said building drum has a central section defining anintermediate portion of the deposition surface.

Preferably said building drum has two half-parts axially positionablewith respect to the central section and defining axially outer terminalportions of the deposition surface.

Preferably said terminal portions have diameter greater than anapplication diameter presented by the intermediate portion.

Preferably said half-parts are slidably engaged around the centralsection. Preferably, said central section is axially fit in radiallyinner position with respect to said half-parts.

The Applicant deems that the substantially concave profile in crosssection consequently conferred to the intermediate portion of thedeposition surface facilitates the execution of the separation of theinternal surfaces of the carcass sleeve from the deposition surfaceitself, for example due to air or another pressurised operating fluidintroduced into the sleeve itself. The subsequent radial expansion forthe purposes of the shaping can thus occur in a uniform and continuousmanner, without the mutual approaching half-parts being able tomechanically interfere with the internal surfaces of the carcass sleeve.Due to the concavity of the profile, the carcass ply/plies, the linerand/or other structural components associated therewith can carry out aslight radial dilatation required for separation purposes, withouthaving to oppose significant mechanical strength and/or be subjected toirregular stresses. A possible anticipation of the introduction of theoperating fluid in the carcass sleeve with respect to the start of themutual approaching of the half-parts, for the purpose of executing theshaping, can therefore be limited to values not greater than about 1-2seconds, or it can even be avoided.

According to a further aspect, the present invention relates to a tyrefor vehicle wheels.

Preferably, said tyre comprises a carcass structure comprising at leastone carcass ply formed by strip-like elements consecutively adjacent oneafter the other according to a circumferential extension and havingoverlap zones along respective longitudinal edges superimposed on eachother. Preferably, each overlap zone has, along a longitudinal extensionthereof, terminal sections that are laterally opposite with respect toan intermediate section.

Preferably, the intermediate section of each overlap zone has greaterwidth than the width of the terminal sections.

In at least one of the aforesaid aspects, the invention also comprisesone or more of the preferred characteristics that are describedhereinbelow.

During the deposition, circumferentially consecutive strip-like elementsare laid one after the other, in such a manner ensuring that a firstlongitudinal edge of the subsequent strip-like element is superimposedon a corresponding second longitudinal edge of the previously laidstrip-like element.

Preferably, the overlap zone has width progressively decreasing awayfrom the intermediate section.

In this manner, a gradual variation of the rigidity of the carcassstructure is obtained in moving away from the shoulder zones towards thebeads, without inducing sudden variations of rigidity in the carcassstructure and consequent localized stresses with potential breakagetriggering.

Preferably, the deposition surface is substantially smooth andcontinuous. Preferably, before forming said at least one carcass ply, atleast one layer-form elastomeric liner is obtained, by deposition of acontinuous elongated element wound according to consecutively adjacentcoils on the deposition surface.

Preferably, the deposition surface has an intermediate portion axiallyinterposed between two terminal portions having diameter greater than anapplication diameter presented by the intermediate portion.

The deposition of the strip-like elements on surface portions withdifferentiated diameter simplifies the obtainment of overlap zones withdifferentiated width in accordance with the design needs.

Preferably, the intermediate section of each overlap zone is arranged onthe intermediate portion of the deposition surface.

Preferably, the terminal sections of each overlap zone are arranged onthe respective terminal portions of the deposition surface.

Preferably, the ratio between the circumferential extension of theterminal portions of the deposition surface and the difference betweenthe circumferential extension of the terminal portions of the depositionsurface and the circumferential extension of the intermediate portion iscomprised between 90 and 110.

It is thus advantageously possible to obtain an optimal reduction of thewidth of the overlap zone in the terminal portions, without causingseparations between circumferentially adjacent strip-like elements.

Preferably, said deposition surface is defined by a building drum havingtwo half-parts axially positionable with respect to a central sectioninterposed between them.

Preferably, the intermediate section of each overlap zone is arranged onthe central section of the building drum.

Preferably, the terminal sections of each overlap zone are arranged onthe respective axially positionable half-parts of the building drum.

Preferably, in said deposition surface the difference between a maximumdiameter of the terminal portions and an application diameter presentedby the intermediate portion is comprised between about 1 and about 10mm.

Preferably, in each overlap zone, the difference between a maximum widthdetectable in the intermediate section and a minimum width detectablealong the terminal sections is less than about 0.5 mm.

Preferably, before the formation of said at least one carcass ply,auxiliary support members, each having at least one circumferentialsupport surface extending on the continuation of the deposition surface,are engaged with the building drum, each in axially approached relationwith regard to one of said half-parts.

Preferably, said at least one carcass ply applied around the depositionsurface has axially opposed end flaps each lying on the circumferentialsupport surface of the respective auxiliary support member.

Preferably, it is provided to form an external annular sleeve,comprising a belt structure.

Preferably, it is provided to shape the carcass sleeve according to asubstantially toroidal configuration, in order to couple it to aradially inner surface of the external annular sleeve.

Preferably, before shaping the carcass sleeve said auxiliary supportmembers are disengaged from the building drum.

Preferably, shaping the carcass sleeve is executed by engaging, with thebuilding drum, a pair of auxiliary shaping members, each in axiallyapproached relation with regard to one of said half-parts.

Preferably, shaping the carcass sleeve comprises feeding an operatingfluid into the carcass sleeve, during a mutual approaching of theannular anchoring structures.

Preferably, shaping the carcass sleeve comprises feeding an operatingfluid into the carcass sleeve, before actuating a mutual approaching ofthe annular anchoring structures.

Preferably, each auxiliary shaping member is engaged with the buildingdrum in replacement of each auxiliary support member, upon removal ofthe same from the building drum.

It is thus possible to provide a building drum with limited weight andsize, that can be easily handled during the building process indifferent work stations, and be adapted for the engagement of theannular anchoring structures and for the execution of the shapingwithout having to remove the carcass structure formed thereon until theend of the building process. Preferably, said at least one carcass plyis locked with respect to annular anchoring structures upon action ofthe auxiliary shaping members.

In such a manner, undesired and uncontrolled movements of the annularanchoring structures and/or structural distortions of the carcassstructure at the beads following shaping are thus avoided.

Preferably, each auxiliary support member is engaged with the buildingdrum at at least one connection member carried by the building drumitself.

Preferably, after the disengagement of the auxiliary support members andbefore the engagement of said auxiliary shaping members at least oneannular anchoring structure is engaged with each end flap of said atleast one carcass ply.

The execution of such action after the disengagement of the auxiliarysupport members facilitates the engagement of the annular anchoringstructures, even if with diameter smaller than the diameter of thedeposition surface.

Preferably, before the engagement of said annular anchoring structures,axially opposed end flaps of said at least one carcass ply are benttowards a geometric axis of the deposition surface.

Preferably, said annular anchoring structures define a fitting diametersmaller than an application diameter defined by the deposition surface.Preferably, said application diameter is greater than or equal to about102% of the fitting diameter.

Preferably, said application diameter is less than or equal to about120% of the fitting diameter.

Advantageously, in such a manner the containment of the deformationimposed on the carcass structure becomes particularly effective. Thelimited stresses imposed on the carcass ply/plies indeed allowminimizing the transverse width of the overlap zones of the strip-likeelements, without the dilatation of the carcass ply/plies during shapingcausing undesired separations between one strip-like element and thenext.

Preferably, each of the strip-like elements laid on the depositionsurface has a longitudinal axis thereof parallel with respect to arotation axis of the building drum.

Preferably, each of the strip-like elements laid on the depositionsurface forms a non-zero angle between a longitudinal axis thereof and aradial plane of the building drum.

Preferably, forming said carcass sleeve comprises:

-   -   forming a first carcass ply; and    -   forming a second carcass ply radially superimposed on the first        carcass ply,    -   wherein the strip-like elements laid for respectively forming        said first and second carcass ply respectively have crossed        longitudinal extensions. Preferably, the intermediate sections        of the overlap zones have an axial size substantially equal to        the axial size of the belt structure.

Preferably, the terminal portions of the deposition surface haverespective frustoconical zones tapered towards respective axially inneredges directed towards said intermediate portion.

Preferably, the deposition surface is substantially smooth andcontinuous. Preferably, coiling devices are configured for laying acontinuous elongated element wound according to consecutively adjacentcoils on the deposition surface.

Preferably, each frustoconical zone has an axial size comprised betweenabout 10 and about 100 mm.

Preferably, each frustoconical zone has an axial size comprised between2 and 50 times the difference between a maximum diameter and a minimumdiameter of the frustoconical zone itself.

Preferably, the ratio between the circumferential extension of theterminal portions of the deposition surface and the difference betweenthe circumferential extension of the terminal portions of the depositionsurface and the circumferential extension of the intermediate portion iscomprised between 90 and 110.

Preferably, in said deposition surface the difference between a maximumdiameter of the terminal portions and an application diameter presentedby the intermediate portion is comprised between about 1 and about 10mm. Preferably, at least one pair of auxiliary support members areremovably engageable with the building drum, in axially approachedrelation each with a respective half-part of the building drum, andhaving respective circumferential support surfaces extending on thecontinuation of said deposition surface in order to support axiallyopposed end flaps of said at least one carcass ply.

Preferably, said circumferential support surfaces have substantiallycylindrical shaping with diameter equal to the diameter of the axiallyouter terminal portions of the deposition surface.

Preferably, second forming devices are configured for forming anexternal annular sleeve, comprising a belt structure.

Preferably, assembling devices are configured for shaping the carcasssleeve according to a substantially toroidal configuration and forcoupling it to a radially inner surface of the external annular sleeve.

Preferably, a pair of auxiliary shaping members are removably engageablewith the building drum, each in axially approached relation with regardto one of said half-parts.

Preferably, each auxiliary shaping member is removably engageable withthe building drum in replacement of said auxiliary support members.

Preferably, said auxiliary shaping members are configured for lockingsaid at least one carcass ply with respect to the annular anchoringstructures. Preferably, each of said auxiliary support members isoperatively engageable with a connection member carried by the buildingdrum.

Preferably, each auxiliary shaping member is removably engageable withthe respective connection member in replacement of one of said auxiliarysupport members.

The Applicant deems it advantageous to arrange a building drumcomprising suitable connection members adapted to be operativelyassociable both with auxiliary support members necessary for the varioussteps for building the different components, and with the aforesaidauxiliary shaping members necessary at the end of building for allowingthe drum itself to attain the shaping of the tyre being processed.

Preferably, the connection members are integrally carried, each by oneof the half-parts of the building drum.

The aforesaid connection members thus standardise the mechanicalassociation of the building drum with devices that are external andseparated therefrom and which are necessary for obtaining the builtgreen tyre, according to the above-illustrated characteristics ofproductivity and flexibility, also decreasing the manufacturingcomplexity of the building drum itself.

Preferably, each overlap zone has width progressively decreasing awayfrom the intermediate section.

Preferably, in each overlap zone, the difference between a maximum widthdetectable in the intermediate section and a minimum width detectablealong the terminal sections is less than about 0.5 mm.

Preferably, a belt structure is associated at a circumferentiallyoutside position to the carcass structure.

Preferably, each of said strip-like elements has a longitudinal axisthereof parallel with respect to a geometric rotation axis of the tyre.

Preferably, each of said strip-like elements forms a non-zero anglebetween a longitudinal axis thereof and a radial plane of the tyre.

Preferably, strip-like elements respectively belonging to a first and toa second carcass ply respectively have crossed longitudinal extensions.

Preferably, the intermediate sections of the overlap zones have an axialsize substantially equal to the axial size of the belt structure.

Further characteristics and advantages will be clearer from the detaileddescription of a preferred but not exclusive embodiment of a process andan apparatus for manufacturing tyres, in accordance with the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Such description will be set forth hereinbelow with reference to the setof drawings, provided only as a non-limiting example, in which:

FIG. 1 schematically shows, in diameter section, a step for applying acarcass ply around a building drum;

FIG. 2 shows, in enlarged scale with respect to FIG. 1, a step in whichannular anchoring structures are coaxially fit on the respective endflaps of the carcass ply/plies;

FIG. 3 shows, in enlarged scale with respect to FIG. 1, a step forturning up the end flaps of the carcass ply/plies around the respectiveannular anchoring structures;

FIG. 4 schematically shows, in diameter section, a carcass sleeve in astep for auxiliary shaping members to engage the beads;

FIG. 5 shows a tyre being processed in the step in which the carcasssleeve is shaped for the application of an external sleeve thereto;

FIG. 6 is a scheme that shows several strip-like elements deposited onthe building drum during the manufacturing of a carcass sleeve inaccordance with the present invention.

DETAILED DESCRIPTION

With reference to the abovementioned figures, reference number 1indicates overall an apparatus for building tyres for vehicle wheels,arranged to actuate a process according to the present invention.

The apparatus 1 is set to manufacture tyres 2 (FIG. 5) essentiallycomprising at least one carcass ply 3 preferably internally covered by alayer of impermeable elastomeric material or so-called liner 4. Twoannular anchoring structures 5, each comprising a so-called bead core 5a preferably carrying an elastomeric filler 5 b in radially outerposition, are engaged with respective end flaps 3 a of the carcassply/plies 3. The annular anchoring structures 5 are integrated inproximity to zones normally identified with the name of “beads” 6, atwhich the engagement normally occurs between the tyre 2 with arespective mounting rim (not depicted), according to a fitting diameterDO determined by the internal diameter sizes of the annular anchoringstructures 5.

A belt structure 7 is circumferentially applied around the carcassply/plies 3, and a tread band 8 is circumferentially superimposed on thebelt structure 7. Two sidewalls 9, each extending from the correspondingbead 6 to a corresponding lateral edge of the tread band 8, are appliedin laterally opposite positions on the carcass ply/plies 3.

The apparatus 1 comprises a building drum 10 having a central section 11axially interposed between two half-parts 12 and extending substantiallyin a relation of surface continuity with respect to the same so as todefine, together with such half-parts in radially outer position, asubstantially smooth and continuous deposition surface 10 a.

The half-parts 12 and the central section 11 are supported by a centralshaft 13 extending along a geometric axis X-X of the building drum 10and of the deposition surface 10 a. Such geometric axis X-X alsocorresponds with a geometric rotation axis of the finished tyre 2.

Identifiable in the deposition surface 10 a are an intermediate portion11 a, defined by the central section 11 and two terminal portions 12 athat are axially outer with respect to the central section 11, definedby the half-parts 12.

The half-parts 12 are slidably engaged around the central section 11. Inother words, the central section 11 is axially fit in radially innerposition with respect to the half-parts 12.

Consequently, the terminal portions 12 a of the deposition surface 10 ahave a maximum diameter Dmax greater than an application diameter D1presented by the intermediate portion 11 a. Preferably, the ratiobetween the circumferential extension of the terminal portions 12 a ofthe deposition surface 10 a and the difference between thecircumferential extension of said terminal portions and thecircumferential extension of the intermediate portion 11 a is comprisedbetween 90 and 110.

The terminal portions 12 a of the deposition surface 10 a, eachdelimited between an axially inner edge 14 and an axially outer edge 15of the respective half-part 12, have respective frustoconical zones 16that are tapered starting from the maximum diameter Dmax up to a minimumdiameter, towards the respective axially inner edges 14 directed towardsthe intermediate portion 11 a. In the illustrated embodiment, theminimum diameter detectable on the axially inner edges 14 substantiallycorresponds to the application diameter D1 detectable on theintermediate portion 11 a.

The difference between the maximum diameter Dmax of the terminalportions 12 a and the application diameter D1 detectable on theintermediate portion 11 a can for example be comprised between 1 and 10mm.

The frustoconical zones 16 can extend according to the entire axial sizeof the respective terminal portions 12 a, or, as represented in theenclosed drawings, they can terminate at a desired distance from therespective axially outer edges 15.

More particularly, it can be provided that each frustoconical zone 16has an axial size comprised for example between 10 and 100 mm.

It can also be provided that the axial size of each frustoconical zone16 is comprised between 2 and 50 times the difference between a maximumdiameter Dmax and the minimum diameter of the frustoconical zone 16itself.

The half-parts 12 are axially positionable with respect to the centralsection 11 and/or axially movable with respect to each other. Forexample, a threaded bar 17 can be operatively arranged within thecentral shaft 13 and carrying two threaded portions 17 a, 17 brespectively clockwise and anti-clockwise, each engaging one of thehalf-parts 12. The half-parts 12 of the building drum 10 areconsequently induced to translate simultaneously in respectivelyopposite directions along the central shaft 13, following rotationsimparted to the threaded bar 17 by means of an actuator (notillustrated) operatively couplable to one end of the central shaft 13.

Each of the half-parts 12 and the central section 11 axially interposedbetween them are preferably composed of respective circumferentialsectors, radially movable between a rest condition and a work condition.In the rest condition (not illustrated), said circumferential sectorsare radially approached to the geometric axis X-X in order to confer thebuilding drum 10 a diameter size smaller than the fitting diameter DO ofthe tyre being processed, in order to allow the removal of the tyre 2from the building drum itself. In the work condition, thecircumferential sectors preferably extend in a relation ofcircumferential continuity, so as to form the aforesaid depositionsurface 10 a, defining an application diameter D1 preferably greaterthan the fitting diameter DO, as in the enclosed figures. Moreparticularly, the application diameter D1 can for example be greaterthan or equal to about 102% of the fitting diameter DO. In a preferredembodiment, the application diameter D1 can for example be smaller thanor equal to about 120% of the fitting diameter DO.

In the illustrated embodiment, the radial movement of thecircumferential sectors is actuated through a plurality of connectingrods 18, each constrained between one of the sectors of the centralsection 11 and a command collar 19, rotatably carried by the centralshaft 13 and drivable in angular rotation by means of an externalactuator (not illustrated). By means of transmission bars 20 axiallyextending through the sectors of the central section 11, the radialmovements of the latter are transmitted to the circumferential sectorsof the axially opposite half-parts 12 of the building drum 10, slidablyguided along respective columns 21 radially extending with respect tothe central shaft 13.

The building drum 10 is adapted to be transferred, by means of at leastone robotic arm (not depicted) or transfer devices of another typeoperating on at least one grip end 13 a presented by the central shaft13, to one or more work stations 22, 23 in order to allow the executionof various processing steps aimed for the assembly of the tyre 2 beingprocessed.

More particularly, the building drum 10 is first engaged in a buildingstation 22 (FIGS. 1 to 3) equipped with first forming devices (notrepresented) configured for obtaining a so-called substantiallycylindrical carcass sleeve 24, comprising the carcass ply/plies 3coupled to the respective annular anchoring structures 5.

At least one external handling device (not depicted since it can beobtained in a known manner), positions auxiliary support members 25 onaxially opposite sides of the building drum 10, each in axiallyapproached relation with regard to one of the half-parts 12.

The auxiliary support members 25, obtained for example in the form oftwo annular elements, externally have respective circumferential supportsurfaces 25 a, having preferably substantially cylindrical shape withdiameter substantially equal to the diameter of the terminal portions 12a. More particularly, the diameter of the circumferential supportsurfaces 25 a preferably coincides with the maximum diameter Dmaxdetectable on the half-parts 12, at the axially outer edges 15. Uponcompleted approaching, the circumferential support surfaces 25 a extendin a relation of continuity on the continuation of the depositionsurface 10 a.

The engagement of the auxiliary support members 25 with the buildingdrum 10 occurs at respective connection members 26 carried by thebuilding drum itself. Preferably each connection member 26, made forexample in cylindrical sleeve form, is integrally carried by one of thehalf-parts 12 of the building drum 10 and operatively couplable with anengagement seat 27 carried by the respective auxiliary support member25.

One or more connection elements 28, obtained for example in the form ofbead-like elements elastically thrust towards the geometric axis X-X,are adapted to be automatically engaged in respective slots arranged inthe connection members 26, so as to retain each auxiliary support member25 in an engagement relation with regard to the building drum 10, evenafter the disengagement of the members themselves by the aforesaidexternal handling device. The building drum 10 is thus adapted to betransferred, if required, between at least one first and one second workunit (not depicted) provided in the building station 22, together withthe auxiliary support members 25 constrained thereto.

In the building station 22, coiling devices (not depicted) can operate,having for example one or more dispensing members that feed at least onecontinuous elongated element made of elastomeric material while thebuilding drum 10 is driven to rotate around its geometric axis X-X, soas to form the layer-form elastomeric liner 4 on the deposition surface10 a and on the circumferential support surfaces 25 a. In addition or asan alternative to the liner 4, the coiling devices and/or otherauxiliary devices can be arranged to form, on the circumferentialsupport surfaces 25 a, anti-abrasive inserts to be incorporated at thebeads 6 and/or, in the case of run-flat tyres, auxiliary support insertsmade of elastomeric material (so-called sidewall-inserts) applied on therespective half-parts 12 of the building drum 10, so as to then beincorporated within the tyre 2 in the zone of the sidewalls 9.

The concavity determined by the difference between the applicationdiameter D1 and the maximum diameter Dmax respectively detectable on theintermediate portion 11 a and on the half-parts 12 of the building drumis also adapted to geometrically accommodate a possible semifinishedproduct made of self-sealing material and/or possible additional layers,applicable at the intermediate portion 11 a before or after thedeposition of the liner 4.

Following the formation of the liner 4, of the abovementioned possibleinserts and/or possible other components, the first forming devicesapply the carcass ply/plies 3 around the deposition surface 10 a. In apreferred embodiment solution, the carcass ply/plies 3 as well aspossibly other parts of the tyre 2 are obtained by deposition ofelementary semifinished products. Such elementary semifinished productsare adapted to be used in a quantity appropriate for composing one ormore of the above-described constituent elements of the tyre, withoutrequiring the storage of semifinished products.

For such purpose, the first forming devices comprise application devicesconfigured for sequentially applying a plurality of strip-like elements29 extending transversely with respect to the circumferential extensionof the deposition surface 10 a, while the building drum 10 is actuatedto rotate according to a step-by-step progression, analogous thatdescribed for example in the document U.S. Pat. No. 6,328,084 on behalfof the same Applicant.

The carcass ply/plies 3 are thus preferably formed directly on thebuilding drum 10, and/or on the possible components previously arrangedthereon. For such purpose, a predetermined number of strip-like elements29 are laid consecutively adjacent one after the other around thecircumferential extension of the deposition surface 10 a, to cover theentire circumferential extension thereof.

Each of the strip-like elements 29 laid on the deposition surface 10 acan have its longitudinal extension axis parallel to the geometric axisX-X. In a different embodiment, each of the strip-like elements 29deposited on the deposition surface 10 a can form a non-zero anglebetween a longitudinal extension thereof and a radial plane passingthrough the geometric axis X-X.

More particularly, the obtainment of the carcass sleeve 24 can providefor the formation of only one carcass ply 3, or two or more carcassplies, in which case the strip-like elements 29 laid for respectivelyforming a first and a second carcass ply 3 preferably respectively havecrossed longitudinal extensions.

During the deposition, circumferentially consecutive strip-like elements29 are laid one after the other, in such a manner ensuring that a firstlongitudinal edge 29 a of the subsequent strip-like element 29 issuperimposed on a corresponding second longitudinal edge 29 b of thepreviously laid strip-like element 29. Mutual overlap zones 30 are thusformed along respective longitudinal edges 29 a, 29 b of therespectively consecutive strip-like elements 29.

Given that the central section 11 of the building drum is slidably fitwithin respective half-parts 12, the deposition surface 10 a assumes aprofile in cross section that is substantially concave. Consequently,also due to the difference between the application diameter D1 and themaximum diameter Dmax respectively detectable on the central section 11and on the half-parts 12 of the building drum, the width of the overlapzone 30 created between each pair of circumferentially adjacentstrip-like elements 29, measurable for example according to acircumferential direction, varies along the longitudinal extension ofthe strip-like elements 29 in accordance with the size variations, interms of diameter and circumferential extension, present along thedeposition surface 10 a, respectively at the central section 11 and atthe half-parts 12.

More particularly, along the longitudinal extension of each overlap zone30, an intermediate section 31 can be identified, arranged at thecentral section 11 and/or at the intermediate portion 11 a of thedeposition surface 10 a, and two terminal sections 32 can be identifiedthat are laterally opposite with respect to the intermediate section 31,at least partially arranged at the respective half-parts 12 and/or atthe terminal portions 12 a of the deposition surface 10 a. Thiscircumstance is better seen in the scheme of FIG. 6, where the overlapzones 30 are shown with hatching, with the differences of widthintentionally amplified.

The intermediate section 31 of each overlap zone 30 has greater widththan the width of the terminal sections 32. Preferably, the differencebetween a maximum width Wmax detectable in the intermediate section 31and a minimum width Wmin detectable along the terminal sections 32 isless than about 0.5 mm. The aforesaid widths are for example detectableaccording to a circumferential direction.

Preferably, at least in the presence of the tapered frustoconical zones16, the overlap zone 30 has width progressively decreasing in movingaway from the intermediate section 31, until it reaches the minimum sizeWmin. The minimum width Wmin of superimposition may assume a zero value,for example at the axially outer edges 15 of the half-parts 12 or at adesired axial distance from the same. Therefore, the mutual overlapzones 30 can extend according to the entire longitudinal extension ofthe strip-like elements 29 or limited to one part thereof.

Preferably, the deposition surface 10 a has an axial size smaller thanthe width of said at least one carcass ply 3, so that the end flaps 3 aof the carcass ply/plies 3 arranged on the building drum 10 axiallyproject from the opposite ends of the deposition surface 10 a and resultat least partially supported by the abovementioned circumferentialsupport surfaces 25 a. At the end flaps 3 a, the overlap zone 30 betweenadjacent strip-like elements 29 preferably maintains the aforesaidminimum width Wmin.

Once the formation of the carcass ply/plies 3 has been completed, theauxiliary support members 25 are disengaged from the respectiveconnection members 26. Such disengagement can be obtained, for example,with the aid of the aforesaid external handling device, by means of asimple action of axial moving away from the respective half-parts 12 ofthe building drum 10, so as to remove the circumferential supportsurfaces 25 a from the anti-abrasive inserts, and/or from the liner 4,and/or from the carcass ply/plies 3.

The removal of the support surfaces 25 a makes it possible, uponpossible transfer of the building drum 10 to a further processing unit,to fold—towards the geometric axis X-X of the building drum 10—the endflaps 3 a of the carcass ply/plies 3 applied around the building drum10; for example, this occurs with the aid of rollers or other membersnot illustrated since they can be obtained in any convenient manner.

Positioning members, not illustrated since obtainable in per se knownmanner, provide to fit each of the annular anchoring structures 5coaxially around one of the end flaps 3 a of the carcass ply/plies 3folded towards the geometric axis X-X, by positioning it in a relationof axial abutment against the corresponding half-part 12 of the buildingdrum 10.

Upon completed positioning, small inflatable chambers 33 or otherturning-up members (FIG. 3) provide to turn up each of the end flaps 3 aaround the respective annular anchoring structure 5, so as to stabilisethe engagement of the same with the carcass ply/plies 3, causing theformation of the aforesaid carcass sleeve 24.

Once the engagement of the annular anchoring structures 5 has beencompleted, or at the same time as this operating step, the applicationof the sidewalls 9 can be actuated.

The building drum 10 carrying the carcass sleeve 24 is then preferablytransferred to the assembly station 23 (FIGS. 4 and 5), which is remotewith respect to the building station 22, in order to receive inengagement an external sleeve 34 integrating the belt structure 7,preferably already coupled with the tread band 8.

The external sleeve 34, having an internal diameter D2 greater than theapplication diameter D1, can be previously prepared by means of secondforming devices, not represented since they can be obtained in a per seknown manner, configured for determining the formation and/or winding ofone or more belt layers adapted to obtain the belt structure 7 on anauxiliary drum (not represented), and the subsequent application of thetread band 8 on the belt structure 7 carried by the auxiliary drum.

According to an alternative embodiment, at least one portion of thesidewalls 9 can be built on the external sleeve 34.

The external sleeve 34 thus formed is adapted to be removed from theauxiliary drum, for example by means of a transfer ring 35 or othersuitable devices that then provide to arrange it in coaxially centeredposition around the carcass sleeve 24 carried by the building drum 10.

Assembling devices then act on the building drum 10 in order to shapethe carcass sleeve 24 according to a toroidal configuration (FIG. 5), soas to determine the coupling thereof to a radially inner surface of theexternal sleeve 34.

The assembling devices can for example comprise the aforesaid actuator(not depicted) arranged to drive in rotation the threaded bar 17, inorder to cause a mutual axial approaching of the half-parts 12 of thebuilding drum 10 and, consequently, of the annular anchoring structures5 of the carcass sleeve 24. Preferably, the assembling devices alsocomprise inflation members having a pneumatic circuit connected to atleast one feed channel 36, obtained for example along the central shaft13, in order to feed an operating fluid into the carcass sleeve 24 andcause the radial expansion thereof by means of inflation, during themutual approaching of the annular anchoring structures 5.

The building drum 10 is then operatively engaged with at least one pairof auxiliary shaping members 37, each in axially approached relationwith regard to one of said half-parts 12. The auxiliary shaping members37 represent components of the apparatus 1 separate from the buildingdrum 10, and are adapted to be integrated with the assembling devices inorder to allow the execution of the step for shaping the carcass sleeve24. More particularly, the auxiliary shaping members 37 are each adaptedto act against a circumferential abutment edge carried by the buildingdrum 10 itself, in order to allow the toroidal shaping of the carcassply/plies 3 at the same time as the mutual approaching movement of thehalf-parts 12.

More particularly, each auxiliary shaping member 37 is adapted to act ina thrust relation against one of the annular anchoring structures 5,each defining one of the aforesaid circumferential abutment edges, inorder to maintain the beads 6 against the building drum 10 and/or lockthe carcass ply/plies 3 with respect to the annular anchoring structures5 during the shaping step, so as to prevent undesired sliding of thecarcass ply/plies themselves or any other undesired deformation in thezones of the beads 6 during the radial expansion of the carcass sleeve24.

Each auxiliary shaping member 37 preferably comprises at least oneflange element 38 removably fixable in axially approached relation withregard to the respective half-part 12 of the building drum 10, andcarrying at least one sealing ring 39 arranged to act against therespective annular anchoring structure 5 carried by the building drum10. Each sealing ring 39, preferably having a continuous circumferentialextension, is also adapted to carry out a function of hermetic sealingclosure of the carcass sleeve 24 at the annular anchoring structures 5,facilitating the radial expansion of the sleeve itself and themaintenance of the inflation state following the shaping step.

Each auxiliary shaping member 37 can be advantageously associated with aplurality of sealing rings 39 that are respectively concentric and haverespectively different diameters. In such a manner, it is advantageouslypossible to use the same auxiliary shaping members 37 for the processingof a vast array of tyres having different fitting diameters.

The auxiliary shaping members 37 can be removably coupled on therespective connection members 26 of the building drum 10, each inreplacement of the respective auxiliary support member 25, by means ofrespective brakes 40, preferably of hydraulic or pneumatic type, eachconfigured for operating on the respective connection member 26 in orderto determine a stable axial anchoring of the auxiliary shaping members37 with respect to the building drum 10.

The combined action of mutual approaching of the half-parts 12 andsimultaneous introduction of air or another fluid into the carcasssleeve 24 brings the latter to progressively expand in radial direction,until it abuts against the radially inner surface of the belt structure7 positioned around the building drum.

The radial expansion of the carcass sleeve 24 for the purposes of theshaping can be preceded by an action of separation of the radiallyinternal surfaces of the carcass sleeve itself from the depositionsurface 10 a, due to the operating fluid introduced in the sleeveitself. The subsequent radial expansion for the purposes of the shapingcan thus be carried out in a uniform and continuous manner, without thehalf-parts 12 in mutual approaching being able to mechanically interferewith the radially inner surfaces of the carcass sleeve 24. Thesubstantially concave profile in cross section of the deposition surface10 a facilitates the execution of this operation. Indeed, due to theconcavity of the profile, the carcass ply/plies 3, the liner 4 and/orother structural components associated therewith can carry out a slightradial movement required for the separation, without having to opposesignificant mechanical strength and/or be subjected to irregularstresses. A possible anticipation of the introduction of the operatingfluid into the carcass sleeve 24 with respect to the start of the mutualapproaching of the half-parts can therefore be limited to values notgreater than about 1-2 seconds, or it can even be avoided.

The axial extension of the intermediate sections 31 substantiallycorresponds with the axial size of the belt structure 7. Consequently,upon completed shaping, as in the finished tyre, the intermediatesections 31 of the overlap zones 30 are substantially extended up to theaxially opposite edges of the belt structure 7. The terminal sections 32of the overlap zones 30 are extended at the sidewalls 9 of the builttyre, starting from the respective axially opposite edges of the beltstructure 7 up to in proximity to the annular anchoring structures 5integrated in the beads 6.

During shaping, the greater width of the overlap zones 30 at theintermediate sections 31 ensures the maintenance of the structuralintegrity of the carcass ply/plies 3, preventing undesired separationsbetween adjacent strip-like elements 29 due to the action ofcircumferential dilatation imposed following the radial expansion.

The smaller width of the overlap zones 30 in the terminal sections 32 isin any case sufficient to ensure the structural integrity of the carcassply/plies 3. Indeed, upon completed shaping, the terminal sections 32 ofthe overlap zones 30 are positioned in the zones extending from theaxially outer edges of the belt structure 7 towards the beads 6, wherethe dilatation imposed due to the shaping is progressively decreasing toa substantially zero value at the reinforcement annular structures 5.

The smaller width of the overlap zones 30 in the respective terminalsections 32 moreover confers a greater structural uniformity to thecarcass sleeve 24, in the zones subjected to greater deformation duringtravel, reducing or eliminating discontinuities of rigidity that can bedetrimental to ride comfort and/or the resistance to the fatiguestresses imposed during the use of the tyre.

Once the shaping step is completed, the brakes 40 can be deactivated inorder to allow the axial removal of the auxiliary shaping members 37from the building drum 10. The building drum 10 can then be possiblytransferred to at least one additional processing station (notdepicted).

Upon completed building, the tyre 2 can be removed from the buildingdrum 10 upon disengagement of the auxiliary shaping members 37 andradial contraction of the drum itself, in order to be subjected to amoulding and vulcanising cycle that can be executed in any convenientmanner.

1. An apparatus for building tyres for vehicle wheels, comprising: firstforming devices configured for forming a carcass sleeve on a buildingdrum, wherein said first forming devices comprise laying devicesconfigured for laying circumferentially consecutive strip-like elementsaround the circumferential extension of a substantially cylindricaldeposition surface presented by the building drum, wherein saiddeposition surface comprises: an intermediate portion extending acrossan axial symmetry plane of the deposition surface and axially interposedbetween two terminal portions, the two terminal portions havingrespective frustoconical zones that are tapered from respective axiallyouter edges defining a maximum diameter of the deposition surface,towards respective axially inner edges directed towards the intermediateportion, wherein the intermediate portion defines an applicationdiameter of the deposition surface at least at said axial symmetryplane, the two terminal portions defining along their entire extension adiameter of the deposition surface that is greater than the applicationdiameter.
 2. The apparatus according to claim 1, wherein the depositionsurface is substantially smooth and continuous.
 3. The apparatusaccording to claim 2, further comprising coiling devices configured forlaying a continuous elongated element wound according to consecutivelyadjacent coils on the deposition surface.
 4. The apparatus according toclaim 3, wherein each frustoconical zone has an axial size comprisedbetween about 10 and about 100 mm.
 5. The apparatus according to claim4, wherein each frustoconical zone has an axial size comprised between 2and 50 times the difference between the maximum diameter and a minimumdiameter of the frustoconical zone itself.
 6. The apparatus according toclaim 5, wherein the ratio between the circumferential extension of theterminal portions of the deposition surface and the difference betweenthe circumferential extension of the terminal portions of the depositionsurface and the circumferential extension of the intermediate portion iscomprised between 90 and
 110. 7. The apparatus according to claim 6,wherein in said deposition surface, the difference between the maximumdiameter of the terminal portions and the application diameter presentedby the intermediate portion is comprised between about 1 and about 10mm.
 8. The apparatus according to claim 7, further comprising at leastone pair of auxiliary support members removably engageable with thebuilding drum, each in an axially approached relation with regard to arespective terminal portion of the building drum, and having respectivecircumferential support surfaces extending on the continuation of saiddeposition surface in order to support axially opposed end flaps of acarcass ply of said at least one carcass sleeve.
 9. The apparatusaccording to claim 8, wherein said circumferential support surfaces havesubstantially cylindrical shape with diameter equal to the maximumdiameter of the deposition surface.
 10. The apparatus according to claim9, further comprising second forming devices, wherein the second formingdevices are configured for forming an external annular sleeve,comprising a belt structure.
 11. The apparatus according to claim 10,further comprising assembling devices, wherein the assembling devicesare configured for shaping the carcass sleeve according to asubstantially toroidal configuration and coupling it to a radially innersurface of the external annular sleeve.
 12. The apparatus according toclaim 11, further comprising a pair of auxiliary shaping membersremovably engageable with the building drum, each in an axiallyapproached relation to one of said terminal portions.
 13. The apparatusaccording to claim 12, wherein each auxiliary shaping member isremovably engageable with the building drum in replacement of saidauxiliary support members.
 14. The apparatus according to claim 13,wherein said auxiliary shaping members are configured for locking saidat least one carcass ply with respect to annular anchoring structures.15. The apparatus according to claim 8, wherein each of said auxiliarysupport members is operatively engageable with a connection membercarried by the building drum.
 16. The apparatus according to claim 15,wherein each auxiliary shaping member is removably engageable with therespective connection member in replacement of one of said auxiliarysupport members.
 17. The apparatus according to claim 16, wherein theconnection members are integrally carried, each by one of the terminalportions of the building drum.